1. Field of the Invention
The present invention relates to an apparatus for easing an impact on a boom of an excavator and a method of controlling the same, which can minimize the impact and vibration occurring in the boom when the operation of a boom cylinder for driving the boom of the excavator is suddenly stopped.
More particularly, the present invention relates to an apparatus for easing an impact on a boom of an excavator and a method of controlling the same, which can minimize the vibration occurring in the boom due to the impact on a boom cylinder by actively controlling an amount of hydraulic fluid being supplied to the boom cylinder when the operation of the boom cylinder is suddenly stopped due to an operator's sudden manipulation of an operation lever for a working device.
2. Description of the Prior Art
Generally, a working device such as a boom of an excavator is driven by manipulating an operation lever. A skilled operator can smoothly operate the working device by precisely manipulating the operation lever, so that an impact on an actuator (e.g., a boom cylinder) can be eased. By contrast, an unskilled operator who has a narrow experience in operation cannot finely manipulate the operation lever, but is apt to suddenly manipulate the operation lever, so that the impact due to the inertia of the working device occurs when the operation lever is suddenly manipulated to lower the working efficiency.
In addition, in the case of suddenly manipulating the operation lever for the working device to improve the working efficiency, vibration is generated due to the impact on the working device during the startup or stop of the working device. This vibration increases the operator's work fatigue to lower the working efficiency, and lowers the durability of the device to shorten the life span of the device.
As shown in FIG. 1, a conventional apparatus for easing an impact on a boom of an excavator includes, a hydraulic pump 50, a pilot pump 53, a boom cylinder 51, connected to the hydraulic pump 50, for being driven when hydraulic fluid is supplied thereto, a main control valve 52, installed in a flow path between the hydraulic pump 50 and the boom cylinder 51, for controlling a startup, stop, and turnabout of the boom cylinder 51, a control valve, installed in a flow path between the pilot pump 53 and the main control valve 52, for being switch when an electric signal is inputted from an outside, and controlling pilot signal pressure being supplied to the main control valve 52, pressure sensors 55 and 56 for detecting operating pressure of a large chamber 51a and a small chamber 51b of the boom cylinder 51, a relay switch 57 for inputting the electric signal to switch a spool of the control valve 54, and a controller 58 for judging whether the boom cylinder has been suddenly stopped in accordance with input signals from the pressure sensors 55 and 56, and if it is judged that the boom cylinder 51 has been suddenly stopped, outputting a drive signal to the relay switch 57.
The controller 58 judges whether the boom cylinder 51 has been suddenly stopped in accordance with the operating pressure values of the large chamber 51a and the small chamber 51b of the boom cylinder 51 outputted from the pressure sensors 55 and 56. If it is judged that the boom cylinder 51 has been suddenly stopped, the controller 58 output the drive signal to the relay switch 57.
The relay switch 57, which has received the drive signal, switches the spool of the control valve 54 to an upper side as shown in the drawing. In this case, the pilot signal pressure discharged from the pilot pump 53 is supplied to the main control valve 52 via the switched control valve 54, and switches the spool of the main control valve 52 to a right side as shown in the drawing.
Accordingly, the hydraulic fluid discharged from the hydraulic pump 50 is supplied to the large chamber 51a of the boom cylinder via the switched main control valve 52. In this case, the hydraulic fluid from the small chamber 51b of the boom cylinder 51 is returned to a hydraulic tank via the main control valve 52.
However, the conventional apparatus for easing an impact on a boom has the problems that in the case where the controller 58 judges that the boom cylinder 51 has been suddenly stopped, a separate relay switch 57 is used to input the electric signal for switching the spool of the control valve 54, and this causes the number of components of the apparatus to be increased with the manufacturing cost increased.